We describe a source-rooted WDM multicast tree construction protocol to support IP dense mode multicast routing protocols in all-optical lambda-switched networks. Using a receiver-initiated approach, the protocol relies on a mechanism that collects information on the capabilities of WDM nodes. This mechanism provides receivers with sufficient information to setup WDM multicast trees in networks consisting of nodes with heterogeneous WDM capabilities. Knowledge of the network topology, group-wide membership information and capability of every WDM network node is not required.